/Engine/Source/Runtime/SlateCore/Public/Input/HittestGrid.h
AddSWidgetfrom the HitTest Grid
void AddWidget ( const [SWidget](API\Runtime\SlateCore\Widgets\SWidget) * InWidget, int32 InBatchPriorityGroup, int32 InLayerId, [FSlateInvalidationWidgetSortOrder](API\Runtime\SlateCore\FastUpdate\FSlateInvalidationWidgetSortOrde-) InSecondarySort )